High MR sensitive fluorescent magnetite nanocluster for stem cell tracking in ischemic mouse brain

Stem cells have shown a great potential to treat diseases and injuries, including ischemic brain injury. However, developing agents for the long-term tracking of stem cells with few side effects is still challenging. Our aim is to develop a novel fluorescent-magnetite-nanocluster (FMNC) with high MRI sensitivity and to examine its application in the labeling and tracking of mesenchymal stem cells (MSC). For this purpose, we developed FMNC by embedding individual magnetite nanoparticles (NPs) into a polystyrene scaffold coated with two layers of silica and a sandwiched layer of rhodamine. We examined the efficacy of FMNC in MSC labeling and the feasibility of tracking FMNC-labeled MSCs in the ischemic mouse brain. We found that FMNC has high cell-labeling efficiency with no adverse effects on MSCs. In a mouse middle cerebral artery occlusion model, FMNC-labeled MSCs migrated to and accumulated in the ischemic region after FMNC-labeled MSC transplantation. MRI findings highly correlated to immunohistochemistry results. From the Clinical Editor: In this study, the authors report a novel fluorescent-magnetite-nanocluster with high MRI sensitivity and to labeling and tracking of mesenchymal stem cells, and provide in vivo data utilizing a murine stroke model. (C) 2011 Elsevier Inc. All rights reserved.